1. Field of the Invention
The present invention relates to an image forming apparatus in which an electrostatic latent image is formed on an image bearing member, for example, by electrophotography and such an electrostatic latent image is visualized with developer by a developing apparatus, and more particularly, it relates to an image forming apparatus including a developer amount detecting device having developer remaining amount detecting means capable of successively detecting a remaining amount of developer contained in a developer container, and a cartridge attachable to such an image forming apparatus, i.e., a process cartridge and a developing apparatus in a form of a cartridge.
The electrophotographic image forming apparatus may include, for example, an electrophotographic copying machine, an electrophotographic printer (for example, an LED printer, a laser beam printer or the like), an electrophotographic facsimile and the like.
Further, the process cartridge is provided by integrally making an electrophotographic photosensitive member and at least one of charging means, developing means, and cleaning means into a cartridge and is detachably attachable to a main body of an electrophotographic image forming apparatus, or is provided by integrally making an electrophotographic photosensitive member and at least developing means into a cartridge and is detachably attachable to a main body of an electrophotographic image forming apparatus.
2. Related Background Art
In the past, a process cartridge in which an electrophotographic photosensitive member and process means acting on the electrophotographic photosensitive member are integrally incorporated as a cartridge unit, which is detachably attachable to a main body of an electrophotographic image forming apparatus, has been used in an image forming apparatus using an electrophotographic image forming process. According to such a process-cartridge system, since the maintenance of the apparatus can be performed by the user (operator) himself without any serviceman, operability can be enhanced considerably. Thus, the process-cartridge system has widely been used in the electrophotographic image forming apparatus.
In the electrophotographic image forming apparatus using such a process-cartridge system, if the developer is used up, although image formation is permitted again by exchanging the empty cartridge for a new one, since the cartridge must be exchanged by the operator himself, it is required that means be provided for informing the operator of the fact that the developer is used up, i.e., a developer amount detecting device should be provided.
Regarding the developer amount detecting device, in order to always know the remaining amount of developer capable of being applied to image formation, developer remaining amount detecting means, capable of detecting a developer remaining amount level, are provided in the cartridge or the main body of the image forming apparatus.
As one of the developer remaining amount detecting means, there is a capacitance detecting system. In this system, an antenna for detecting the developer remaining amount is located within a developer container, and the remaining amount of the developer is detected by utilizing a change in current generated in the antenna in accordance with the amount of the developer between an electrode and the antenna when AC voltage is applied to an electrode provided at a predetermined location.
For example, as an example using a capacitance detecting system, there is a flat antenna system. As shown in FIG. 3, a flat antenna 20 is obtained by forming a pair of conductive patterns 22, 23 on a substrate 21 with a predetermined interval, and, for example, the flat antenna is located at a position where it contacts developer at the side surface of the developer container so that the contact area between the developer and the flat antenna 20 is decreased as the developer in the developer container is decreased.
The capacitance is changed by the change in the contact area between the conductive pattern surface and the developer as a result of consumption of the developer. Thus, the remaining amount of the developer in the container can correspond to the capacitance of the flat antenna, with the result that the remaining amount of the developer in the container can always be known by measuring the capacitance of the flat antenna.
The capacitance of the flat antenna 20 can be determined from current flowing through one of a pair of conductive portions 22, 23 when a predetermined AC bias is applied to the other conductive portion.
Further, as another example using the capacitance detecting system, there is a plate antenna system constituted by a metal plate (plate antenna) disposed in parallel with a developing roller as a developer carrying member provided within a developer container, in a so-called jumping developing system in which a latent image on a photosensitive member is developed by applying an AC bias to the developing roller.
The plate antenna system utilizes the fact that the capacitance between the plate antenna and the developing roller is changed in accordance with an amount of the developer existing between the plate antenna and the developing roller. If a space between the plate antenna and the developing roller is filled with the developer, the capacitance becomes great, and, as the amount of the developer is decreased, the amount of air between the plate antenna and the developing roller is increased, thereby decreasing the capacitance. Accordingly, by previously determining the relationship between the capacitance between the plate antenna and the developing roller and the amount of the developer, the amount of the developer can be known.
In a method for measuring the capacitance, the capacitance can be sought by measuring current flowing through the plate antenna when the AC bias, as a developing bias, is applied to the developing roller. Namely, the developer remaining amount detecting system can detect the remaining amount of the developer during image formation in which the developing bias is being applied to the developing roller.
By providing the above-mentioned developer remaining amount detecting means on a developer containing portion, i.e., the developer container, the amount of the developer capable of being supplied for the image formation can always be known, and, at the same time, it can always be known how many copies can be obtained from now.
Further, as the developer remaining amount detecting means, there is a torque detecting system in which developer agitating means are provided within a developer container and the remaining amount of developer is detected by utilizing a change in the load acting on the developer agitating means in accordance with the remaining amount of the developer.
However, in all of the above-mentioned developer remaining amount detecting systems, although the developer remaining amount level can be detected, satisfactory detecting accuracy cannot be obtained due to a limitation on the measurement resolving power and measuring error.
In particular, there is a need for means capable of effecting display with high resolving power (resolution) when the exchanging time of the process cartridge approaches and capable of correctly detecting the developer remaining amount whenever the process cartridge is exchanged.
The present invention relates to further improvement of such an image forming apparatus and a process cartridge detachably attachable (mountable) to the image forming apparatus.
The present invention aims to eliminate the abovementioned conventional drawbacks, and an object of the present invention is to provide an image forming apparatus and a cartridge detachably attachable to such as image forming apparatus, in which the remaining amount of developer can be detected correctly.
Another object of the present invention is to provide an image forming apparatus and a cartridge detachably attachable to such as image forming apparatus, in which the remaining amount of developer can be displayed correctly.
A further object of the present invention is to provide an image forming apparatus and a cartridge detachably attachable to such as image forming apparatus, in which the remaining amount of developer can be displayed with a high resolving power.
A still further object of the present invention is to provide an image forming apparatus comprising a developer container for containing a developer, developer amount detecting means for detecting the amount of the developer contained in the developer container, consumed amount calculating means for calculating the consumed amount of the developer, and remaining amount calculating means for calculating the remaining amount of the developer from the output of the detecting means and the output of the consumed amount calculating means.
A further object of the present invention is to provide a cartridge comprising a developer container, and a memory for storing information regarding an amount of developer detected by detecting means for detecting the amount of the developer contained in the developer container and information calculated by consumed amount calculating means for calculating a consumed amount of the developer.
The other objects and features of the present invention will be apparent from the following detailed explanation of the intention referring to the accompanying drawings.